Facsimile system and apparatus



March 19, 1946. s. KHAUL FACSIMILE SYSTEM AND APPARATUS Filed Jan. 29.19 6 Sheets-Sheet 1 S. KHAL".

AT TOR N EY March 19, 1946. s. KHALIL FACSIMILE SYSTEH AND APPARATUS 6sheets-meet:

Fi1ed Jan. 29. 1943 FIG.

8. KHALIL ATTOR N EY March 19, 1946. '1 s. KHALIL" I 2,396,705

FACSIMILE SYSTEM AND APPARATUS Ema Jan. 29, 1945 v e Sheet Sheet sINVENTOR s. KHALIL ATTORNEY S. KHALlL FACSIMILE SYSTEM AND APPARATUS Iarch 19, 1946.

Filed Jan. 29, 1945 s Sheets-Sheet 5 FE. m

' INVENTOR s. KHALH.

' ATTORNEY March 19, 1946. s. KHALIL 2,

FAcs1MILE sis'rEM AND APPARATUS r I a .6 Sheets-Sheet 6 FIG. I4

Filed Jan. 29, 1945 ATTORNEY .7 G) I INVENTOR 207 Patented STATE2,396,105 FACSIMILE SYSTEM AND APPARATUS Application January 29, 1943,Serial No. 473,896

33 Claims. The present invention relates primarily to facsimile systemsand apparatus therefor and more particularly to novel and improvedtransmitting and receiving facsimile machines and a novel synchronizingsystem employing the same for transmitting and receiving subject mattersuch as pictures and messages in facsimile.

There have been several types of facsimile machines proposed heretoforeandv they may be classified in two general classes, the unilateral orunidirectional type wherein the direction of movement of the scanningelement relative to the material scanned is always in-the'samedirection, and the bilateral or back-and-forth type wherein the scanningelement moves back-and-forth or in two directions relative to thematerial scanned.

The so-called cylinder machine is the most generalsof the firsttypewherein the subject matter sheet in the transmitter and therecording blank in the receiver are wrapped around cylinders and ascanning element in the transmitter and a recording element in thereceiving machine move axially of the cylinders as the same rotate.

A lead screw is usually provided to produce relative movement betweenthe rotating cylinders and the scanning or recording elements, andaccordingly the movement of the scanning and re= producing elementsrelative to their respective cylinders is unidirectional and theelements trace a continuous helix on the cylinders. Inasmuch as nocorrection or synchronization is ordinarily applied to the rotatingdrums during the scan ning and reproducing of a subject matter sheet,any difierence in speeds of the drums will have an accumulative adverseefiect on the fidelity of the reproduction. In addition to the above,the cylinder type of facsimile machine has the disadvantage thatconsiderable care must be exercised in placing the subject matter sheetsand the recording blanks on the cylinders.

Another type of unidirectional facsimile machine sometimes employed,primarily as a receiving instrument, isthe type wherein the recordingblank is maintained flat and a plurality of recording styli arranged onan endless belt to successively contact the recording blank one at" atime to reproduce .the subject matter. This type of machine has thedisadvantage that it can only be used as a receiving instrument and likethe cylinder type any speed difference between the driving means .for itand the transmitter will adversely affect the reproduction.

In this type or machine, as in the cylinder type. if the transmitterandreceiver aregoing at dittravel.

ferent speeds, the received copy will be skewed, that is, a verticalline for example or one substantially at right angles to the directionof the movement of the scanning element will be reproduced as a slantingline. If the transmitter is faster, the line will slope in one directionand if thereceiver is faster, the line will slope in the otherdirection. If the speed of either the transmitter or receiver varieswith respect to one another during the scanning of a subject mattersheet, and the speeds are different, vertical lines will be reproducedassloping lines with various degrees of curvature, the degree of curvaturedepending upon the variation of relative speeds.

In the bilateral type of machine, the scanning element moves back andforth and performs a scanning operation during each direction of its Thescanning element is usually driven by a cam and insome types of machinesthe cam is released at the beginning of the scanning of a subject mattersheet while in others the cams for controlling the scanning elements aresynchronized periodically or after each forward and back stroke of theelements. In this type of machine wherein the'driving means for thescanning elements are not synchronized after each forward and backstroke, any speed diilerence between the receiver and transmitter wouldhave an accumulative adverse effect on the reproduction. If the speed ofthe transmitter and receiver are difierent and constant, a singlevertical line for example on the subject matter in this type of machinewill be recorded as two broken or dotted lines at an angle to eachother, so that the two dotted lines will form a V. In a bilateral typeof machine that is synchronized with the transmitter after each strokeor after each combined forward and back stroke of the scanning element,if there is a speed difierence between the transmitter and receiver, asingle vertical line on the subject matter will be recorded either as azig-zag line or as two brokenor dotted parallel lines on thereproduction. The varying of the speed of the driving means during arecording operation of either the transmitter or receiver in the abovementioned bilateral types of machines will also have an adverse effecton the reproduction, the distortion indicated above being modified bycurvature of the two broken lines or by an increase in the amount ofdeviation of the zig-zag line.

From the above it is seen that any speed difierence or variation in thedriving means for a transmitter and receiver in a facsimile system hasanadverse effect on the fidelity of the reproduction and it isaccordingly one of the primary objects of this invention to provide afacsimile system and apparatus wherein these adverse eifects areentirely eliminated or if not eliminated, reduced to a negligibleminimum and as is the case with machines which are not periodicallysynchronized, to provide a machine wherein the speed difference andvariation does not have an accumulative adverse effect on-thefaithfulness or fidelity of the reproduction.

The present invention is illustrated in the accompanying drawings andhereinafter described as being applied to a facsimile transmittingmachine wherein the subject matter is held flat and the scanning elementmoved back and forth relative thereto to perform a scanning operationduring each direction of its travel. In a similar manner the recordingstylus or element in the receiving instrument moves back and forthrelative to a flat recording paper to perform a recording functionduring each direction of its travel. Although the invention is shown andde scribed in conjunction with one particular type of machine, it willbe apparent that it is not so limited but that the principles thereofmay be applied to various other types. In the described embodiment ofthe invention, the subject matter in the transmitting instrument and therecording paper in the receiving instrument pref erably move in adirection perpendicular to the direction of movement of the scanning andrecordingelements intermittently at the end of each stroke of theirrespective elements.

- In the present invention synchronization between the transmittingandreceiving-mechanisms is maintained in a novel and improved manner,and as will be obvious hereinafter has man advantages over prior artdevices.and systems. In the present arrangement the scanning elements orthe scanning heads of the two machines, the transmitter and thereceiver, are started in the same direction at the same instant. Sometime during the first scanning stroke the direction of movement of thescanning heads is simultaneously reversed and, as the speed of theindividual driving means of the scanning heads will not vary appreciablyand can be assumed to remain substantially constant during a singleoscillation of the scanning heads, they will reach their initialposition at exactly the same time. However, should the speed of eitherone or both of the driving means vary during an oscillation of thescanning elements, there would not be an accumulative adverse effect onthe reproduction, as will be apparent hereinafter. With the presentarrangement the speed of movement of the two individual scanning headsmay be substantially different from one another, but since they arestarted simultaneously and the direction of movement of the two heads isreversed at the same time they will reach'their initial positions atsubstantiall the same time even though one head may" travel a greaterdistance than the other. In other words, the scanning heads starttogether and move in one direction distances that are proportional tothe speed of the individual driving means, and after a certain length oftime the direction of movement of the two scanning heads issimultaneously reversed. Since the speed of the driving means of thetwo' heads may be assumed to remain constant, they will reach theirinitial pos tion simultaneously so as to start the scanning of thefollowing line together. Any speed difference between the: driving meansfor ing element would be a difference in one dimension of the size ofthe reproduction relative to the subject matter.

With a facsimile machine wherein the line scanning isperformed as aboveand the line feed effected intermittently with the scanning operation, avertical line, for example, on the subject matter will be reproduced onthe recording blank as a vertical line with no distortion thereof ordrift. Also, any horizontal line, for example, will be reproduced as ahorizontal line on the record ing blank, and lines perpendicular to oneanother on the subject matter, as for example, vertical and horizontallines, will be reproduced exactly perpendicular to one another on therecording blank. Such a system of facsimile reproduction has manyobvious advantages and uses over the systems employed heretofore.

With a machine and system such as described above, enlargements orreductions of the subject matter may readily be made on the recordingblank b changing the speed of the scanning head of the receivingmechanism relative to the speed of the scanning head of the transmittertogether with an appropriate change in the line feeding mechanism.

.In view of the inherent limitations and disadvantages of prior artfacsimile machines and systems, it is one of the objects of the presentinvention to provide facsimile transmitting and receiving equipmentwherein exact synchronism between the driving means is not essential forthe proper operation of the machines and the reproduction of a.reasonably exact facsimile of the subject matter.

Another object of the present invention is to;

provde transmitting and recording facsimile machines and control meanstherefor to operate and control the scanning and recording elements inthe proper timerelation to one another whereby substantially exactreproduction of the subject matter is produced at the receiver.

Another object of the invention is to provide transmitting and receivingfacsimile mechanism wherein the subject matter to be transmitted suchas-pictures or messages ,may be maintained in a fiat condition duringtransmission and. in which the recording medium may also be maintainedin a flat condition during reception.

Another object of the present invention is to provide facsimilemechanism wherein the subject matter scanned movesin a directionperpendicular to the scanning movement and preferably duringnon-scanning condition of the scanning element.

A still further object of the invention is to pro-- vide mechanismwhereby the recording medium is moved perpendicularly relative to thedirection of the recording movement of the recording element andpreferably during. a non-recording condition thereof.

Another object of the present invention is to provide a facsimile systemwherein the time consumed in performing a certain operation in thelength of the lines scanned in both machines.

Another object of the invention is to provide facsimile transmitting andreceiving mechanisms adapted to operate in accordance with a system asoutlined above.

Another object of the invention is to provide facsimile machines adaptedto operate on the above arrangement wherein the scanning elements have abi-lateral or back and forth scanning movement relative to the subjectmatter and recording sheets.

Another object of the invention is to provide a correcting mechanism fora bi-lateral scanning facsimile machine whereby the time elapsingbetweenthe beginning of the scanning of successive lines is equalized.

Another object ofthe invention is to provide a correcting mechanism fora bi-lateral scanning facsimile sytem wherein correction is applied to ascanning'element of either a receiver or transmitting instrument at theend of one .stroke, for example, in proportion to the speed differencebetween the two scanning elements so that with I a correcting mechanismfor a bi-lateral scanning facsimile machine wherein correction may beapplied to both the transmitter and receiver scanning elements at theend of the first strokes thereof, for example, in proportion with thespeed the speeds remaining constant the said scanning difference betweenthe two elements and a given standard so that with the speeds remainingconstant the scanning elements reach the ends of the next strokes insynchronism with the given standard.

Another object of the invention is to provide a rotating facsimilescanning element driving means arranged, for example, to* make one-halfA revolution in one scanning stroke of the machine and correct therotation of the driving element at the end of one-half revolutionin'proportion to the speed difierence thereof and a given standardduring the said one-half revolution to enable the rotating element withthe speed thereof remaining constant to reach an initial position insynchronism with the given standard.

In accordance with the above, it is a still further object of theinvention to provide means for rotating the facsimile scanning elementdriving means in a reverse direction after one-half revolution thereofan amount proportional to the speed difference between it.and a givenstandard during the said one-half revolution.

successively scanned. A lens system is employed in conjunction with thelight beam in the usual manner and also a chopper disc which interruptsthe light beam at a certain frequency to generate a carrier frequency.The tonal densities of the subject matter modulate the carrier frequencyin proportion to the amount of light reflected from the scanned subjectmatter. In the preferred embodiment of the transmitting and receivingmechanisms, the scanning element and-the recording element move back andforth in a scanning and recording movement relative to the subjectmatter and the recording medium, while the so-called line feed of thesubject matter and recording medium is in a direction perpendicular tothe scanning and recording movements.

The recording element in the recording mechanism preferably consists ofa stylus which duplicates the movement of the scanning element in thetransmitting machine and reproduces a facsimile of the subject matter.The recording medium itself preferably is of the type which is adaptedto change the color characteristic thereof on the passage of an electriccurrent therethrough, the current passing through the paper beingmodulated in accordance with the subject 'matter scanned.

The preferred embodiment of the invention employs a reversing clutch forreversing the direction of movement of the scanning element in thetransmitter and the recording element in the receiver. The reversingmechanisms may be controlled by any suitable means such as clock workswhich may be maintained in synchronism and A still further object of theinvention is to provide a facsimile system and transmitting andreceiving instruments to operate in conjunction therewith in such amanner that any speed difference, whether variable or constant. betweenthe driving means for the said instruments does thereof.

The transmitting mechanism employed in the preferred embodiment of theinvention employs a photocell in its scanning element, and a pencil orbeam of light is directed on the subject matter so as to reflect on thephotocell to excite the same in accordance with :the tonal densities ofthe subject matter as elemental areas thereof are corrected periodicallyfrom the transmitter or receiver or from a control point. A modifiedrevers ing or correcting mechanism employs a so-called differentialarrangement whereby difierences in speed of thedriving means-of thetransmitter and receiver are corrected in amounts proportional to.

the diflerence in speed of'the two driving means, or in amountsproportional to their speed and a given standard. The correction. occursperiodically, and there is no accumulative effect on the reproduction ofspeed difference between the receiving and transmitting mechanisms or agiven standard.

A more thorough understanding of the invention may be had from thefollowing detailed description of the preferred and one modifiedembodiment thereof when taken in conjunction with the accompanyingdrawings, in which:

Fig. l is a diagrammatic view of a facsimile sytem'employing themechanism of the present invention;

Fig. 2 is a perspective view of the principal elements of a facsimilemachine constructed and controlled in accordance with the presentinvention;

Fig. 3 is a view showing the path of relative movement between thescanning element and the subject matter in the transmitting mechanism orthe recording element and the recording medium in the receivingmechanism;

Fig. 4 is a detail view of some of the elements of the reversing clutchemployed to reverse the direction of movement of the scanning elementsuch as employed in Fig. 2;

Fig. 5 is a right hand view of the elements shown in Fig. 4; Fig. a is adetail view of the control mechanism employed to owrate the reversingmechanism;

Fig. 7 is a perspective view of the invention adapted to be controlledin accordance with the operation of the modified reversing mechanismemploying the so-called differential correcting mechanism;

Fig. 8 is a diagrammatic representation of a modified control circuitfor a facsimile system embodying mechanisms of the present invention;

Fig. 9 is a detail view partly in section of the differential correctingmechanism;

Fig. 10 is a detail view taken substantially on line |8|6 of Fig. 9;

Fig. 11 is a vertical sectional view taken substantially on line of Fig.9;

Fig. 12 is a left hand end view of some of the mechanism shown in Fig.9; and

Figs. 13 to 18 are diagrammatic views of the differential correctingmechanism shown in Figs.

. 9 to 11 illustrating the principles of operation thereof.

Referring first to Fig. 2 there are shown the elements included in theembodiment chosen to illustrate the invention. As will be pointed outhereinafter, and as will beapparent from the appended claims, theinvention is not'limited to the particular arrangement shown in thedrawings but may be incorporated in many other arrangements. In thearrangement shown in Fig. 2 a flat table 2| is supported on a base 22and arranged to move longitudinally relative to the base being guided bymeans such as 23 in the base and projections 24 on the underside of thetable.

The table 2| has thereon the subject matter sheet 26 to be scanned, andit may be a message, map or picture, etc. Clamping members 21 may beemployed to hold the sheet 26 to the top of the table. As will beapparent, the mechanism disclosed in Fig. 2, while being describedprimarily as a transmitting machine, may be employed equally well as arecording machine, in which case the subject matter sheet 26 would bereplaced by a recording blank. Attached to the table 2| is one end of aflexible band 28, the other end of which is arranged to wind up about aspring drum 29. The spring drum 29 may be of the type em ployed toadvance the carriage in an ordinary typewriter and contains a spring(not shown) normally tending to rotate the drum in a clock wise.direction, as shown in Fig.. 2. The spring drum 29 through the flexibleband 28 tends to move the table 2| in the direction indicated by thearrow 3| but is normally prevented from doing so by means hereinafterdescribed. The spring drum 29 is provided with some means such as theknob 32 whereby the tension of the spring drum tending to advance thetable may be varied.

Depending from the right hand side of the table 2| and extending thefull length thereof is a rack 33 which is engaged by a pinion 34. Thepinion 34 is mounted on a shaft 36 suitably supported in bearings (notshown) and has fixed to escapement wheel 41 the forward end thereof agear 31. The gear 31 meshes with a smaller gear 38 on a shaft 39 whichalso has fixed thereto a toothed ratchet disc 4|. In axial alignmentwith the shaft 39 is a second shaft 42 which carries a multi-toothedcamdisc 43. Extending axially from the back side of the cam disc 43 is apin 44 which carries a pawl 46 held by a spring 45 in engagement-withthe teeth of the ratchet wheel 4|. The spring drum 29 tends to advancethe table 2| in a line spacing direction and at the same time tends torotate the toothed ratchet wheel 4| through the described gear trainincluding gears 38, 31, the pinion 34 and rack 33. Because of the pawl46 and ratchet wheel 4|, the table 2| may be moved either manually or bysuitable automatic means in a direction opposite to the arrow 3| for thepurpose of resetting the table without effecting rotation of the shaft42. This operation will, of course, be performed-prior to the beginningof the scanning of a subject matter sheet 26 and restores the tension tothe spring in the spring drum 29.

Fixed to the forward end of the shaft 42 is a toothed escapement wheel41 which has in operative relation therewith an escapement yoke,indicated generally by reference numeral 48, having arms 49 and 5|positioned on the right and left hand sides, respectively, of theescapement wheel. The escapement yoke 48 is pivotally mounted on a pin52, and a complete oscillation comprising movement in one direction andthen in the opposite direction permits rotation of the escapement wheel41 one tooth. A stroke or half oscillation of the yoke 48 permitsrotation of the half the distance between adjacent teeth in the mannercommonly employed in clock works.

The timing of the oscillations of the yoke 48 is controlled by a timingmeans including a flywheel 53 loosely mounted on a shaft 54. Theflywheel 53 has one end of a hair spring 56 attached thereto, theopposite end of which is secured to the shaft 54. The flywheel 53 alsocarries a pin 51 extending axiall therefrom which engages thebifurcation 6| in the lower end of the escapement yoke 48. Theescapement wheel 41, tending to rotate from power derived from thespring drum 29, causes the escapement yoke 41 to oscillate, and thetiming of the oscillations is controlled by the flywheel 53 and attachedspring 56. For each half oscillation of the escapement yoke 48 the table2| is advanced a predetermined distance in the direction of the arrow3|, and this advancement of the table is hereinafter referred to as theline feed advancement. The distance the table 2| advances for each halfoscillation of the escapement yoke 48 is determined by the relative sizeof the gears 31 and 38 and the pinion 34. Preferably this advancement ofthe table is in steps of approximately one onehundredth of an inch so asto give scanning lines on one-hundredth of an inch apart. Obviously thedistance the table advances for each half oscillation of the escapementyoke may readily be varied by changing the relative size of the gears 31and 38 or by changing other elements of the advancing mechanism. It willalso be obvious that the above-described mechanism effects advancementof the table 2| in intermittent steps.

and these preferably occur, as will'hereinafter be pointed out, duringthe non-scanning part of the movement of the scanning head or scanningelemerit. The timing period of the escapement yoke .48 is determinedprimarily by the tension of the supported on a pin 69 and has anarmature 1| at its left hand end inoperative relation withelectromagnets 12. A spring 13 normally pivo s an amount equal to one--interrupting the light beam I Notion-8i to engage the flywheel 63, andif at this time the center of the notch 66 is anywhere else butdirectlyover the wedge-shaped projection 67, the flywheel will berotated in either direction as the projection 61 enters the notch 88.Such operation of the electromagnets 12 co!- rects the position of theflywheel 53 in a'manner more fully described hereinafter and effectsthis correction to advance the flywheel if it is slow or to reset thesame if it is fast. The amount the' flywheel 53 may be fast or slow isdetermined by the portion of the periphery of the flywheel that thenotch 86 includes. While this portion is shown in the drawings tocomprise only a small portion of the periphery of the flywheel 53, as itis expected only a small correction will be necessary, the design of theflywheel could be changed so that the correction could effectsubstantial parts of a revolution thereof. y

The actual scanning operation of the subject matter sheet in thetransmitter and the recording blank in the receiver preferably occuralternately with a line feed operation, and in the embodiments shownherein the scanning elements are arranged to move relative to the table2| to perform a scanningoperation. However, as will be apparent, thescanning element could be maintained stationary and the table moved backand forth in one direction for scanning movement and longitudinally in adifferent direction for line feeding. In Fig. 2 the scanning element isrepresented by the so-called scanning head 14 and it is adapted to movetransversely of the subject matter sheet 26 on guide rods such as I6.The scanning head M of Fig. 2 would preferably include as shown in Fig.1, a source of light 11, a chopper disc 19, and the photocell I9together with the lens system which would include lenses such as 8!. Asshown in Fig. 1, the light beam from the source TI is directed at thesubject matter sheet 28 to successively illuminate elemental areasthereof and the light is reflected onto the photocell I9 in accordancewith the tonal densities of the subject matter. The chopper disc I8 at auniform rate generates a carrier frequency which is modulated inaccordance with the tonal densities of the subject matter.

The output of the photocell which varies in accordance with the tonaldensities of the elemental areas of the subject matter is applied to anamplifier represented by therectangle 82 of suitable design whichcontrols the transmission of signals representing the subject matterover the line circuit such as 83. The line circu't 83 may be of any ofthe well known types and for the sake of simplicity only thesingleconnection is shown.

At the receiving end of the line-circuit 83 is another amplifying means84 which operates in the usual manner to apply modulated electricalpotential over the conductor 88 to a recordin means such as a stylus81-. The amplifier 84 applies the modulated potential to the stylusaccordance with the modulated carrier frequency.

' The recording medium 88 has the elemental areas successively scannedby the stylus such as 81 and is supported on a conducting plate which inthe arrangement shown in grounded. The recording medium 88 may be of thewell known type such as disclosed in a patent to R. J. Wise et al. No.2,294,147, issued August 25, 1942, that changes the stylus, there willbe reproduced thereon an image similar to that on the subject mattersheet 28. Obviously, either of the amplifiers would contain a signalinverter if desired so that the reproduction would not be a negative ofthe subject matter. scanned. The diagrammatic showing in Fig. 1 alsoincludes various control elements hereinafter described in detail whichare employed to maintain the proper relation between the transmittingand receiving machines.

If the ing instrument, the scanning head I8 thereof would contain arecording stylus such as 81 of Fig. 1 instead of the light beam,photocell'and related elements. Preferably, of a machine would containboth the scanning light beam and photocell with its related equipmentand a recording element or stylus such as 81 so that the machine couldbe used either as a transmitter or a receiver,-of course, only one ofthe elements, the scanning element or the recording element, being usedat a time. p j

The mechanism for moving the scanning head 14 back and forth over thetable will now be described. This mechanism includes two spring 2,normally tending to rodrums 89 and 9|, Fig. tate in the direction of thearrows adjacent thereto to wind-up about the circumferences thereofassociated flexible bands 92 and'93. The flexible band 92 passes'over anidler pulley 94 and has the end thereof attached to the left hand sideof the scanning head 14 while the flexible band 93 attached to the righthand side of the scanning head passes over an idler pulley 96 and thento its associated spring drum 9|. As shown'in more detail in Figs. 4 and5, the spring drums 89 and 9| are pivotally mounted onindependent'shafts such as 91 and rotatable with the spring drums 89 and9| are associated wheels 98 and 99 re- 99 one at a time is a drivewheelI9I. During the scanning of a. subject matter sheet the drive wheel |8|is arranged to be constantly rotated through elements hereinafterdescribed and is brought into engagement first with one wheel 98 or 99and then the other to rotate the same independently and wind theflexible bands 92 and 93 about the associated spring drums. The windingof the band 92 about the spring drum 89 causes the'scanning head I4 tomove to the left and during such time the band 93 unwinds from itsassociated spring drum 9|. The subsequent engagement of the drive wheelIIlI with the wheel 99 causes the flexible band 93 to wind up about itsspring drum 9| and move the scanning head in the opposite band 92 isunwinding from its drum. Themovement of the drive wheel |I||from'engagement with one wheel such as 98 to the other such as 99 iscontrolled. by the escapement mechanism which also controls the linefeed 'movement of the table.

The drive wheel I9| which also has thereon .a gear I03. The shaft I82 issupportedin the upper end of alever I98 pivotally mounted adjacent itscenter on a shaft I88. The shaft I86, as shown in Figs. 2, 4 and 5, issuitably journaled in a stationary part of the framework indicatedgenerally by reference numeral I 91. Mounted on the shaft I95 is a gearI98 which machine shown in Fig. 2 were a receiv-- the scanning head 98and.

direction to the right while the.

is mounted on a shaft I82 ence numeral III,

. shown in Fig. 4. In this position the meshes with the previouslymentioned gear I03 and drives the same. The shaft I06 is driven from amotor drive shaft pinion I09 of a motor M and a gear IIO throughanelectromagnetcontrolled clutch indicated in general by refer- Themagnet 2 controls the clutch III in a manner hereinafter described.

The lower end of the lever I04 has a pin II 3 extending therefrom whichengages a slot H4 in a jockey lever H5. The jockey lever H5 is pivotallymounted adjacent its center on a fixed pivot H6 and has attached to theupper end thereof the upper end of a jockey spring I II. The

lower end of the spring III is anchored on a pin H8 in verticalalignment with the shaft I06 and the fixed pivot H3. The jockey lever inconjunction with the spring- III biases the drive wheel- IOI into eitherone of its operative positions.

A pin II 9 located in the lever I 04 above the center pivot pointengages a slot I2I in the left hand end of a link I 22. The link I22 isattached at its right hand end to the upwardly extending arm of a bellcrank I23 which is pivotally mounted in a fixed pivot I24. Therightwardly extendingarm of the bell crank I23 is engaged by abifurcated left hand end as shown in Fig. 6 of a lever I26. The leverI26 is pivoted at its right hand end on a fixed pivot I27 and has to theleft of the pivot a cam follower I28 in operative relation with theperiphery of the cam disc 43. A spring I29 holds the cam follower I28 inengagement with the disc 43.

The cam disc 43 is stepped in the manner hereinbefore described amountsequal to one-half the distance between successive teeth on theescapement disc 41. The cam disc 43 has projections such as I 3I equalin number to the teeth on the escapement disc and. after each step ofthe disc 43 either a projection I3I or a notch between two projectionswill be in engagement with the cam follower I28. Accordingly, the leverI26 will be oscillated up and down so as to make one movement for eachstep of the escapement disc 47. The movement of the lever I26 from itslower position as shown in Fig. 6'to its upper position as shown -by thedotdashed outline thereof will rock the bell crank I23, Fig. 4,.in acounterclockwise direction. This causes the link I22 to push on the pinII 9 and rock the lever I04 in a counter-clockwise direction. Duringthis movement of the'jlever I04 the jockey lever H5 is also rocked inaf'counter-clockwise direction to increase the tension in the jockeyspring I I I and when the end of the jockey lever to which the spring isattached is just beyond dead center, the spring is effective to snap thejockey lever to its other position. Thus the movement of the lever I04which is initiated by the link I 22 is d. by the jockey lever I I5 andattached spring II1, the slot I 2i in the left hand end of the lever I22 permitting movement of the lever I I5 independently of the link'l22In a similar manner the rocking of the bell crank I23 in a clockwisedirection by the lever I26 pivots the lever I04 in a clockwise directionto the position drive wheel IOI carried in the upper end of the leverI04 is in engagement with the wheel 99 associated with the spring drum9|, is pivoted in the opposite direction, the drive wheel IN is in itsother position and engages the wheel 98 as shown by the fragmentarydotted portion thereof in Fig. 4.

whereas when the lever I04 the drive wheel ner engagement of the drivewheel with the wheel 98 moves the scanning head to the left. The springssuch as I32, Fig. 4, in the spring drums 89 and 9!, preferably arearranged so that the tensions thereof may be varied by well knownsuitable means such as manually positionabw members I33. The tensions ofthe springs 1r, said drums are preferably adjusted so that they exert anequal tension on their associated flexible bands when the scanning head14 is in substantiallythe center of its travel. When the flexible bandwinds up aboutone spring as controlled by the drive wheel II, thetension of the spring in the spring drum from which the band isunwinding is increased. This difference in tension of the springs in thespring drum which will occur when the scanning head I4 is near eitherend of its travel, assists in overcoming the inertia necessary to startthe scanning head for the beginning of a scanning movement in anopposite direction to its last scanning stroke. However, IUI is arrangedto move from one position. to the other extremely fast and during suchmovement the difierence in tensions of the springs in the spring drums89 and SI preferably do not cause any independent movement of thescanning head I4, I

From the above arrangement it is obvious that reciprocating movement ofthe scanning head I4 is produced and that during its movement it willhave, within the limitations of the driving motor, substantiallyuniformspeed in each direction. Accordingly, a scanning function may beperformed during each movement of the scanning head and time is not lostas is the case in some facsimile machines wherein the scanning elementreturns to a normal position at the beginning of a line'by anon-scanning return movement following each scanning movement. It willalso be obvious that the above arrangement has the advantage that bychanging the sizes of the wheels such as 93 and 99, the length of a linescanned in each scanning function may be varied while the timecharacteristics of the control mechanism are maintained constant. Thelength of the scanning line may also be varied by maintaining theproportions of the scanning head driving elements fixed and varying thetime characteristics of the escapement control mechanism.

The advancement of the table 2I, Fig. 2, in a line spacing direction,preferably occurs during the operation of the reversing mechanism whichincludes the drive wheel I0 I, or while the scanning element in thescanning head is scanning the margin of the subject matter sheet andtable, and is adapted to occur substantially instantaneously. Thisarrangement produces a scanning of the subject matter sheet 20asexemplified in Fig. 3 Where the dot-dashed line I34 represents therelative movement between the scanning head such as 74 and thesubject-matter sheet 26. If the scanning head I4 is assumed to start ata point I 36 and then travel to the right across the subject mattersheet to the point I31, at which time the table 2I is advanced onescanning line, then the return scanning stroke of the scanning head willtraverse the second dot-dashed line on the sheet 26, Fig. 3. Thisproduces scanning lines which are exactly parallel with one another andin a direction perpendicular to the direction of movement of the subjectmatter sheet.- This arrangement has many obvious advantages over themethod and mechanisms employed wherein the subject matter sheet iswrapped around a cylinder and scanned in one continuous helix or methodswherein the subject matter sheet is scanned by prior art arrangements..

The modified arrangement of the invention employs a so-calleddifferential reversing mechanism, and this mechanism will now bedescribed. The application of the differential mechanism to a machinesuch asdisclosed in Fig. 2 is shown in Fig. 1, and as will be apparentmany of the elements of Fig. 7 are. identical with those of Fig. 2 and,accordingly, bear and are referred to by the same reference numerals.The differential mechanism itself may be enclosed within the box I46,Fig. '1, and the power therefor supplied from a constantly rotatingmotor M of suitable speed characteristics through an electromagnetcontrolled clut'ch I45 including a control magnet I44.

The control of the reversing mechanism is effected through a lever I48which is operated from a cam disc 43' included in the escapementmechanism. The escapernent mechanism of the arrangement shown in Fig. 7is somewhat the same as that of.

Fig. 2, with the exceptions hereinafter pointed out. The cam disc 43' inFig. 7 has twice as many projections thereon as the teeth on itsassociated escapement wheel 41, and the escapement yoke '48 is pivotableon a pivot pin I42 at the lower end thereof under the control ofseparate electromagnets I43. With this arrangement the escapement yoke48' is operated as the magnets I43 are alternately energized to escapethe wheel 41 a half tooth for each movement of the yoke or one tooth foreach complete back and forth oscillation thereof. The lever I48 isoperated momentarily by the disc 43' once for each half toothadvancement of the escapement wheel 41.

The reversing mechanism will be described in detail hereinafter, but forthe present it is be-,

lieved desirable to describe the connection thereof with the scanninghead 14. As shown in Fig. 7, the reversing mechanism has a crank arm I49at the forward end thereof to which is connected a link II. The link I5Iis pivotally attached to a block I52 adjustable along-a slot I53 in alever I54. The lever I54 is pivoted at its lower end on a pivot pin I56, and the upper end has connected thereto a link I51. The other end ofthe link I51 is attached to a pin I58 extending from a spring drum I59.The spring drum I59, together with a second spring drum I6 I, ispreferably of larger diameter than the spring drum 89 and 9| of Fig. 2,

and the reason for'this will be obvious hereinafter.

Bands 92 and 93 connect the scanning head 14 to preferred thereofefiects a complete scanning movement in one direction of the scanninghead 14. As in the embodiment, the tension of the springs in thespringdrums I59 and I6I, Fig. 7, is such that they exert substantially equalforces on the scanning head 14 when it is in the middle of its traveL.With such an arrangement the unequal tensions of the springs in thespring drums when the scanning head reaches the end of a stroke tends toovercome the inertia thereof in initiating a return stroke. By adjustingthe position of the v block I52 along the slot I53 in the lever I54, the

amount of oscillation of the lever I54 may be varied, which in turn willvary the stroke of the scanning head 14. The pin I62 in the bl ck I52 isadapted to engage holes such as I63 in the lever I54 to lock the blockin an adjusted position.

Referring now to Figs. 9 to 12, the details of the elements of thereversing mechanism will now be described. Included in this mechanism isa shaft I64 which is driven from the motor M through suitable reductiongearing, if desired, and through the electromagnet clutch I whichincludes the control magnet I44, Fig. 7. The shaft I 64 is suitablyjournaled in bearing supports such as I66 and has adjacent its righthandend. as shown in Fig. 9, a threaded portion I61 preferably having-amultiple lead. Mounted on the threaded portion I61 of the shaft I64 is asleeve I68 which has formed integrally therewith a socalled stop discI69. A radial flange IN is formed in the lefthand end of the sleeve I68and adapted to engage the right hand side of this flange are twodiametrically opposite pins I12 The upper end of the yoke I13 is pivotedat I14 in a rightwardly extending arm of a member I16 attached by meansof a screw I11 to the shaft I64 for rotation therewith. A spring I15anchored in the member I16 and attached to the yoke I13 tends to pivotthe yoke in a clockwise direction and keeps the pins I12 against theflange I1I. The lower end of the yoke I13, as shown in Fig. 9, ispivotally connected to theright hand .end of a link I18,.the left handend of which is pivotally and adjustably connected adjacent the centerof a lever I19. The lever I19 is pivotally mounted at its lower end on aleftwardly extending arm of the memthe spring drums I59 and I6I and tendtowind up' about the spring drums due to the action of the springscontained therein.

As the crank arm I49 of the reversingmechanism rotates, the link I5Iattached thereto causes the lever I54 to pivot back and forth, and itthrough the link I51 turns the spring drum I59 a predetermined amount inone direction and then an equal amount in the opposite direction.

. As the spring drum I59 is turned in one direction scanning head 14will move to the right due to the as,' for example,.a counterclockwisedirection, the

action-of the tension on the flexible band 93. The rotation of thespring drum I59 in the opposite direction causes its flexible band 92'to wind up about the circumference thereof to move the scanning head 14to the left. The diameter of the spring drums, and especially the springdrum I59, such that approximately 120 ro ation her I16, which arm isdiametrically opposite to the rightwardly extending arm thereof to whichthe upper end'of the yoke I13 is pivotally attached. The upper endof-thelever I19 is U- shaped and carries pins I8I which are located in acircular groove I82 in the right hand end of a cam member'I83. v

The cam member I83 is loosely mounted on the shaft I64 and is axiallymovable thereon in a manner hereinafter described. The cam membercarries a. pin I84 which engages a helical groove I86 formed in theshaft I84 so that axial movement of the cam member along the shaftproduces relative rotation between the two elements. The lead of thegroove I86 is not the same as the lead of the threaded portion I61 ofthe shaft I64 for reasons that will be apparent. Formed integrally withthe cam member I83 adjacent the left hand end is a disc I81 withdiametrically opposite notches I88 in theperiphery thereof which-engagepins I89. The pins I89 ex-' tend axially from the right hand side of adisc I9I looselymounted on the left hand end of the shaft I64 androtatable independently thereof. The pin shaped end of a screwl92 in thedisc I9I engages a circular groove I 93 in the shaft I64 to preventaxial movement of thedisc I!" on the hand end thereof by screws such asI94 is the hereinbeforementioned crank arm I49, which has attachedthereto the link I I.

As shown more clearly in Fig. 10, the stop disc I 69 has extending fromthe periphery thereof two diametrically opposite stop surfaces orprojections I 95 and I96. In operative relation with the stop surfacesI95 and I96 is a T-shaped stop member I91 which is pivotally mounted ona pin I98 in the upper end of a lever, I99 pivotally mounted on a fixedpivot 20I. A spring 202 normally biases the stop member I91 to a stopdisc stopping positionor in the path of the stop surfaces or projectionsI95 and I 96, as limited by a stop pin 203.

Extending from the lever I99 is a pin 204 which is engaged by the upperbifurcated end of a lever 206 secured at its lower end to a rock shaft201 supported in brackets 208. Also secured to the rock shaft 201 is a.leftwardly extending arm 209 which, as best shown in Fig. 11, has a slot2I2 in the left hand end thereof which engages a pin in the lower end ofa rod 2I3. The rod 2I3 is guided for vertical movement in a portion 2Mof the bracket member and has at its upper end a roller cam follower 2I6engageable with the central surface of the cam member I83. roundingtherod 2 I 3 tends to elevate the said rod to keep the cam follower 2 I6 inengagement with the periphery of the cam member I83. As shown in Fig.11, the cam member I83 has two diametrically opposed notches or recesses2I8 therein so that, as the same rotates, the rod 2 a downward directiontwice for each complete revolution of the cam member I83.

In addition to the making of the stop member I91, Fig. 10, about thepivot I98 due to the operation of the lever I48, as hereinafterdescribed.

the stop member moves back and forth in the direction of its lengthtwice for each revolution of the cam member I83 through theinstrumentalities of the above-described elements including the notchesin the cam member I83, the rod 2I1, arm 209, lever 206 and lever I99.Thus, the stop projections I95 and I96 on the stop disc I 69 areengageable with the stop member I91 at a point variable distances aheadof the normal zero position shown in Fig. 10. In accordance with theproportions of the various elements, the stop projections I95 and I96may engage the stop member I 91 at any point between the normal stopposition shown by the full outline thereof in Fig. 10 and thedot-dashedposition shown.

The correcting mechanism or the differential A sprin 2I1 sur-,

I3 is moved inreversing mechanism in the box I 66, Fig. 7, is sodesigned that when associated with a receiving instrument for example,and the shaft I 64 in exact synchronism with the driving shaft on atransmitting mechanism and/or the clock control elements, there is nofunctional or correcting operation of the elements comprising thedifferential reversing mechanism, as will be evident. The cam surfacesor notches 2I8 in the cam member I63 and the operating element for thestop member I91 are so arranged that the above-described lateralmovement of the stop member from left to right and right to left is atthe same speed as the peripheral speed of the stop projections I95 andI96 when rotating with the shaft I64. If the receiver is in exactsynchronism with the transmitter or the synchronizing-mechanism, memberI91 is pivot point pivoted by the lever I46 about the I98 just as thestop projection I95 rothe stop tates into its so-called zero position,as shown in Fig. 10. At the same time a notch 2I8 in the cam member I83begins to move the stop member I91 laterally toward the left. The stopmember I91 reaches the position shown by the dot-dashed outline thereofafter approximately 30 rotation of the cam member I83 from its zeroposition and remains in this position for the time being. If it isassumed that it requires 30 rotation of the cam member to move the stopmember to some such position as shown by the dot-dashed outline thereofin Fig. 10, then it will require 150 rotation of the stop disc I 69 fromits zero position before the stop projection I96 rotates to a positionwhere it is engageable with the end of the stop member I91.

Just as the stop projection I96 reaches the left hand end of the stopmember I 91, the other notch 2I8 of the cam member I83 is operative toeffect movement of the stop member to the right. As the notch 2 I8 isdesigned to produce lateral movement of the stop member toward the rightat a speed substantially equal to the peripheral speed of the stopprojections I 95 and I96, the stop memher will have no effect inreducing the speed of rotation of the stop disc I 69. Accordingly, thestop projection I96 and the stop member I91 will move to the righttogether with no functional engagement between the two. With the assumedcondition of exact synchronism between the receiving and transmittinginstrument, the lever I48-will pivot the stop member I91 about the pivotI96 just as the stop projection I96 reaches the position occupied by thestop member I95 in Fig. 10, and there will be no stopping orreduction-in speed of the stop disc I 69 during the first halfrevolution thereof. If the speed of the shaft I64 remains in synchronismwith the transmitting mechanism, there will be no stopping or reductionin speed of the stop disc I69 during the .second half revolution thereofor at theend of first half revolution. Thus, as long as the shaft I64remains in synchronism with the transmitting mechanism, there is nostopping or slowing down of the stop disc I69 once it is initiated intorotation until the completion of the scanning of a subject mattersheet.- For the above-described operation there is no functionaloperation of the correcting mechanism, and obviously the scanning headsof the transmitting and receiving mechanisms are in exact synchronismwith each other and both scan respective elemental areas of the subjectmatter spectively. With such tical line, for instance, on the subjectmatter would be produced as a vertical line on the recording blank, andthere will be no drift or sloping of the reproduced line on therecording blank. In addition, such a mechanism as described. wherein theline feedin -of the subject matter and recording blank is effectedduring non-scanning operation of the mechanism, all horizontal lines,for example, are reproduced strictly horizontal on the recording blank.Furthermore, it will be obvious that lines which are perpendicular toeach other on the subject matter, such as vertical and horizontal lines,are produced exactly perpendicular to each other on the recording blank.If the scanning strokes of the transmitting and receiving machines areequal and the and recording blank, re-

line feeding mechanisms adapted to advance the an arrangement any ver- 4before the stop member I91 same amount on each operation, the recordingblank will be an exact reproduction in all dimensions of the subjectmatter.

The operation of the differential mechanism is considerably difierentfrom that described above when there is a speed difference between thetransmitting and receiving mechanisms. The manner of operation of thereversing mechanism will now be described when, speed of rotation of thethe speed of rotation of the shaft employed to operate the transmittingmechanism. It will be assumed for the following description that theshaft I64, which is rotating faster than the similar shaft On thetransmitting mechanism where the synchronizing impulses originate, ,isat constant speed.

In Figs. 13 to 18 there is diagrammatically shown the operation ofvarious elements of the correcting mechanism, and in these figures likereference numerals refer to like elements shown in Figs. 9 to 12. Thestop disc I69 is shown in its zero position in Fig. 13, and the stopmember I91 by the full outline thereof in the position it will assumeafter it has been pivoted by the escapement mechanism including thelever I48. After 150 rotation of the stop disc I69 from its zeroposition with the proportions of the elements as shown, the stopprojection I96 reaches the position shown in Fig. 14 in operativerelation with the end of the stop member I91 which has been moved to theleft. Thereupon or during the next 30 rotation of the stop disc I69, thestop projection I96 rotates to the position shown in Fig. 15, while theleft hand'end of the stop member I91 moves from its left hand positioninto the position shown in Fig. 15. As previously described, the notches2I8 in the cam member I83 effect movement of the stop member I91 to theright at a speed substantially equal to the peripheral speed of a stopprojection such as I96, and accordingly there is no operative engagementbetween the stop projection I96 and the end of the stop member I91during the for example, theshaft I64 is faster than reach the positionshown in Fig. 15 after 169 revolution thereof and for obvious reasonsthe correcting mechanism operates at that time in such a manner thattheamount of correction applied to the disc is proportional to the amountthat the stop disc was fast in the first half cycle. With thisarrangement the stop disc will complete a revolution and reach its zeroposition in exact synchronism with the synchronizing mechanism, it beingassumed that the speed of the shaft I64 remains substantially constantfor one revolution or that the speed variation is such as to be of noconsequence.

As the stop disc in Fig. 15, the stop projection I96 will engage theleft hand end of the stop member I91 to be stopped thereat. As the shaftI64 continues to rotate, the collar I68, Fig. 9, immediately begins tothread along the threaded portion I61 of the shaft I64. Preferably thethreaded portion I61 is multiple threaded and the movement of the collarI68 axially of the shaft I64 permits the spring I15 through the yokeI13, link I18 and lever I19 to slide the cam member I63 in a leftwarddirection along the axis of the shaft. The leftward movement of the cammember I83 produces rotation said rightward movement. If it is assumedthat t the rotation of the stop disc I69 from the position shown in Fig.13 to the position shown in Fig.

15 occurred while the corresponding element-on the transmittingmechanism rotated but 110, then the receiving stop disc I69 at this timewould be 1 ahead of the transmitting stop disc. Accord-.

ingly, the stop disc I69 on the receiving mechanism should be correctedwhile the transmitting disc rotates 1 and, in addition, should beoperated upon to effect a correction for the next or second halfrevolution of the stop disc of the transmitting mechanism. Correction iseffected by retating the stop disc I69 on the receiving mechanism in areverse direction an amount proportional'to the speed diifere'ncebetween the two rotating elements or in proportion to the amount thereceiving stop disc was ahead of the stop disc on the transmittingmechanism in the first half revolution of the stop disc of thetransmitting mechanism. Thus the stop disc I69 on the receivingmechanism will have to, in its second half cycle of operation, rotate180 plus an amount pro-'- portional to the speed difference between thereceiving and transmitting mechanisms.

With the-shaft I64, for example, on'the receiv-- ing mechanism rotatingfast or at such a rate that it completes a revolution before theoperation of v the synchronizing mechanism, the stop disc I69 will be inthe position such as that shown in Fig.

has been pivoted about the pivot point I98. The stop disc I69 will 76rotate the thereof relative to the in a direction ppposite to thedirection of rotation of the shaft I64. As the cam member I83 rotates inthe reverse direction, the mechanism comprising the rod 2I3, arms 269and 266, and lever I99 moves the pivot point I98 for the stop member I91to the left as shown in Figs. 10 and 13 to 18. The leftward movement ofthe stop member I91 rotates the stop disc I69 in a reverse directionrelative to the direction of rotation of the shaft I64 so as to producemore axial movement thereof relative to the shaft which in turn throughthe described linkage produces further axial movement of the cam memberI83. The various elements above mentioned are so designed and arrangedthat the leftward movement of the stop member begins substantiallyinstantaneously with the stopping of the stop disc I69 in the positionshown in Fig. 15 or its position after 180 rotation. The elements arealso so arranged that the rate of rotation of the stop disc I69 in areverse direction is exactly the same as the rate of rotation of theshaft I64 in the opposite direction.

The rotation of the stop disc I69 in a reverse direction will continueuntil the stop member I91 .is operated so as to pivot about the pivotpoint I96 in response to the synchronizing mechanism by some means suchas the operating lever I48. When the stop member I91 is thus operated,the stop disc I69 and the cam member I83 will rotate with the shaft I64,'and assuming the speed of the shaft I64 remains constant, the stopdisc will reach its zero position in exact synchronism with the trippingmechanism or just as the stop mem ber I81 is operating the next time.The spring I15 tending to move the sleeve I68, Fig. 9, to the leftinsures thatthe sleeve will rotate with the shaft I64 when not stoppedby the engagement of a stop projection I95 or I96 with the stop memberI91.

Let it be ass'un'ed, for example, that'the movement of the stop memberI91 to the left before being operated by the lever I48 was such as tostop disc I69 in a reverse direction,

I69 reaches the position shown shaft I64 by means of the j that asthecam member 186 moves to the'le'ft, the same will be caused to rotatedisc I69 is in its zero the stop disc is merely chosen to illustrate theprinciples of operation of the correcting mechanism and actually only asmall fraction of such an amount would normally be required. However,the correcting mechanism could operate in such amounts or more ifrequired. If the stop member I91 operates when the stop disc I69 is insome position such as shown in Figs. 16 and 17, then the cam follower 2I 6 will be in some position other than in the bottom of the notch 2I8in the cam member I83. Therefore, as the cam member I83 resumes itsrotation with the shaft I64, the stop member I9! while still in areleasing position will move to the right the same distance it moved tothe left to correct the rotation of the stop disc and then will move tothe left to its extreme left hand position such as shown in Figz18. Whenthe stop projection I95 reaches the stop member I91; then it will moveto the right and as the stop projection I95 reaches its zero position,the stop member will be operated in the manner hereinbefore describedwithout retarding the rotation of the stop disc at this time. The amountof correction applied to the stop disc I69 or the amount it is rotatedin a reverse direction is such that it will complete a revolution and bein its'zero position at exactly the time of the operation of thesynchronizing mechanism or at the time the member I48 is operated topivot the stop Since the stop disc I69, the cam member I83 and the crankarm, I49 all rotate together, the amount of correction applied riedthrough to the crank arm I49. The elements operated by crank arm I 49are so arranged that they are in one extreme position when the stopposition and in their other extreme position when the stop disc hasrotated the associated instrument will be in one extreme position whenthe stop disc I69 is in its zero poscanning or non-recording interval.In addition the correction to the'crank arm I49 is applied when it is indead center position relative to the elements operated thereby and itmay be moved or corrected a considerable amount before havon thescanning head.

recting mechanism it was assumed that the synchronizing impulsesoriginated at the transmitting mechanism which was operating withoutcorrection being applied thereto or was operating at such-a speed thatit'completed, a half revolution in exact synchronism with the operation01' the synchronizing mechanism.- The correction applied to thereceiving mechanism was such that it completed a complete revolution nexactly the length of time required for the transmitting mechmember IS!a second time.

to the stop disc I69 is car-' Thus, the scanning head ofasoaroa anism tocomplete a revolution. Thus, the two mechanisms start a cycle ofoperation or a cycle in which while the transmitting mechanism isscanning an elementary area on the subject matter, the respect to thespeed cording mechanism is scanning a representative area on therecording blank, and this is true during both the forward and backwardmovement of the scanning heads.

Should both the transmitting and receiving mechanisms be going fasterthan the synchronizing mechanisms, they will both be corrected inamounts proportional to the amount they are faster than thesynchronizing mechanism in the manner described above. Thus, regardlessof the respective speeds, the scanning heads of both machines will starttheir forward strokes'and finish their backward strokes together.

In the above description the speed of the driving means for thereceiver, while being faster than the speed of the driving means for thetransmitter, was constant. For this condition the amount of correctionapplied after one-half revolution of the stop disc I69 in the receivinginstrument, Fig. 9, was such that it completed the next half revolutionin exact synchronism withthe transmitting instrument, it being assumedthat the transmitting instru-- ment was in exactsynchronism with thesynchronizing impulse transmitting means or that the synchronizingmechanism was operated in conjunction with the transmitting instrument.The diflerential mechanism will function, however, if the speed of thdriving means varies with reof the synchronizing impulse transmittingmeans or with respect to the driving means for the instrument where thesynchronizing signals originate. If, for example, the speed of the stopdisc I69'during the second half of a revolution thereof is faster thanthe speed of ro- In the above described operation of the cor- 5 5 hertans operated,

the first and second th above condition tation during the first halfrevolution, the stop disc will reach its zero position, such as shown inFig. 13, prior to the releasing operation of the stop member I91. Thestop member I91, as hereinbefore described, will immediately begin tomove to the left to correct the stop disc an amount proportional to thehalf revolutions thereof. For the amount of correction applied to thestop disc I69 after a complete revolution thereof, or with the disc I69in its zero position, will not correct for the entire speed differencethe driving means of the transmitting and receiving instruments, or thespeed difierence between the shaft I64 and the synchronizing impulsetransmitting means, but for the speed difference between the first andsecond half revolution of the stop disc I69. noted when the speed of thedriving means is increasing relative to the synchronizing impulsetransmitting means at its zero and one-half revolution positions. Thecorrection to the disc I66 will continue to be applied in the samecontinues to increase in speed relative to the synchronizing impulsesand in its 'one-hali' revolution position because of the speeddifference between the synchronizing impulses and the driving means ofthe'disc I69. If th disc I69 is rotating faster than the synchronizingmechanism and b gins to lose speed relative thereto, the stop projectionI will not quite reach its zero position when the stop memandaccordingly the stop disc it was assumed that i,

difference in speed between Thus, the stop disc I 69 would be coritszero position as will reach its zeroposition a' little late or by anamount proportional to the decrease in speed between the first andsecond half revolutions thereof. Accordingly, it will take it a slightlylonger interval for the disc I69 to reach its next half revolutionposition, and the correction ordinarily applied at this point, providedthe speed of the disc is still faster than the synchronizing impulses,will not be so much as it would be if the speed had remained constant.This decrease in the amount of correction applied at the half revolutionpoint accounts for the decrease in speed of the disc I69, and thedecrease in speed will not have an accumulative effect on the positionof the stop disc I69 relative to the time of transmission of thesynchronizing impulse. Thus, as long as the speed of the stop disc I69remains faster than the synchronizing impulses, it may vary in eitherdirection, and th correcting mechanism will operate to effect acorrection in the position of the stop disc relative to thesynchronizing impulses.

The above correction prevails on the receiving instrument whether thesynchronizing impulses originate with the transmitting instrument orfrom a separate control point. Where the synchronizing signals originatefrom a synchronizing impulse transmitting means separate from thetransmitting and receiving instruments, they both will be corrected inthe above-described manner when the speeds thereof are different fromthat of the synchronizing mechanism or when the speeds are varyingrelative to the synchronizing mechanism. When the synchronizing impulsesoriginate independently of either the transmitting or receivinginstruments, the speed of the driving means of one instrument may beincreasing while the speed of the driving means of the other instrumentis decreasing, and appropriate corrections will be applied to theirrespective stop discs such as I69.

Mention has been made hereinbefore in connection with the description ofthe various elements of the invention of synchronizing impulses whichare employed to maintain proper synchronism between the transmitting andreceivinginstruments of a facsimile system as disclosed herein. As willbe apparent hereinafter, these synchronizing impulses may originate atthe transmitter, the receiving, orat a point independent of both thetransmitter and receiver. control circuits included in the presentinvention will now be given as they are arranged when the synchronizingimpulses originate in conjunction with the operation of the transmittingmechanism. Referring to Fig. 1, there are shown the control elements ofa transmitting instrument and those of a receiving instrument connectedby the line The description of the r conductor 83. The escapement yoke48 on the transmitting instrument, as shown, has associated therewith aset of contacts 22I which are adapted to be closed when the escapementyoke oscillates into its left hand position and to be open with the yokein any other position. One of the terminals of the contacts 22I isconnected to the movable arm'222 of a manually .operable switch 223, andthe other terminal of the contacts is connected by a conductor 224through the coil of a three-position polar relay 226 tothe amplifier 82.The relay 226 is of the type that on the passage of current of onepolarity therethrough the associated tongue 22! is operated to contactone stop, and with the passage of current of opposite polaritytherethrough, the tongue is operated to contact the other stop, and withthepassage of no current through the relay the tongue 221 assumes acentral position in contact with neither of its associated stops. Theleft hand stop of the tongue 221 of relay 226, to which stop the tongueis moved on the passage of negative current through the relay, isconnected through the coil of a relay 228 to ground. The relay 228 hastwo tongues connected to positive potential, and the make stop of theinner tongue is connected through the coil of the clutch control magnetII2 to ground, while the make stop of the outer tongue of relay 228 isconnected through the coil of magnet 12 to ground. The movable arm 222of the switch 223 has two associated stops, the left hand one of whichis connected to negative potential and the right hand one to positivepotential. With the movable arm 222 on its right hand stop a positiveimpulse will be transmitted therefrom through the contacts 22I overconductor 224 through the coil of relay 226, the amplifier 82, to theline circuit 83, each closed.

The grounded relay 229 connected to the amplifier 84 Y operation to therelay 226 at the transmitting station and responds to control impulsestransmitted over the line circuit 83. The tongue 23I of relay 229contacts its right hand stop on the passage of negative potentialthrough the winding and its left hand stop onthe passage of positivepotential through the winding. When there is no current through thewinding of the relay 229, the tongue 23I assumes a central position incontact with neither of its stops. The tongue 23I of relay 229 isconnected to positive potential, and its associated left hand stop isconnected to the make stop of the outer tongue of a relay 232 inparallel with thewinding of the magnet I2 to ground; The right hand stopof the tongue 23I of relay 229 is connected through the coil of relay232 to ground. The tongues of relay 232 are connected to positivpotential, and the-make stop of the inner tongue is connected throughthe coil of a I clutch control magnet II2 to ground.

Let it be assumed that the arm 222 of the switch 223 is on its left handstop and that the contacts 22I are closed by the yoke 48 being in itsleft hand position. The yoke -48 is held in this position by meanshereinafter described. Accordingly, negative potential from the lefthand stop of switch 223 will be applied through the contacts 22I andthrough the relays 226 and 229 to ground.

As hereinbefore described, negative potential'operates the tongues ofrelays 226 and 229 to their left and right hand stops, respectively.With the tongue 22! of relay 226 on its left hand stop, relay 228 will benergized, causing its tongues to complete circuits through magnets H2and 12 to energize the same. The energization of the clutch controlmagnet II2 operates the clutch III, Fig. 2, to disconnect the drivewheel IIlI from the motor M. Theenergization of magnet 12 operates thearmature lever 68 to force th projection 61 into the notch in theflywheel 53. This holds the flywheel 53 and escapement yoke 48 at restin a non-operating position, and in this position the contacts 22I areheld closed. In addition to disconnecting the drive wheel IllI from themotor M,

' the operation of the magnetic clutch III preferably prevents furtherrotation of the drive wheel. With the tongue 23I of relay 229 at thereceiving station on its right hand contact, relay 232.

time the contacts 22I are at the'receiving station is similar contactsits right hand periodic energization of the magnet 12 engages theflywheel doctor 83 the associated escapement yoke 48 to stop in itsnon-operating position, while the energization of the clutch controlmagnet H2 disengages the drive motor from the associated drive wheel atthe receiving instrument in a similar manner, as the energization ofmagnet H2 at the transmitting station controls the clutch HI thereat.The instruments at both the transmitting and receiving stations are thusheld in non-operating conditions with the respective elements thereof inthe same relative positions. To initiate the operation of the twomachines to scan a subject matter sheet.

and reproduce a facsimile thereof at the receiving instrument, thetablesand scanning heads, if not already in a starting position, may be soplaced and the switch 221i operated to place its movable arm in contactwith its right hand stop. This operation impresses positive potential onthe windings of relays 226 and 229, whereupon the tongues thereof moveto their right and left hand stops, respectively. As tongue 22'! ofrelay 226 stop, the circuit through relay 228 is interrupted, whereuponthe tongues thereof open the circuit to the clutch control mag net H2and the magnet 12. Th deenergization of the clutch control magnet H2renders the associated clutch l l I, Fig. 2, operative to connect themotor M with the drive wheel ii, and the deenergization of magnet 72releases the flywheel 53 to permit the escapement yoke 48 to oscillate.The escapement yoke 48 will continue to oscillate as timed by theflywheel 53, and at the end of each complete oscillation or as it movesinto its left hand position, the contacts 22I will be closed momentarilyto reapply positive potential over the line circuit 83, Fig. 1, to therelay 229 at the receiving station.

The movement of the tongue 23l of relay 229 from its right hand stopopens the circuit to relay 232, which in turn opens the circuitscompleted on the energization thereof to magnets H2 and 12'. Preferably,the relay 232 does not release until after the tongue of relay 229 hasreached and left its left hand stop. Accordingly, magnets 12' and H2 Thedeenergization of the clutch control magnet H2 connects the drive wheelsuch as Hll at the receiver with the motor M and. initiates scanningmovement of the associated scanning head containing the recording stylus81. tion of magnet 12' releases the flywheel 53 at the receivinginstrument and permits the escapement yoke to oscillate and shift thedrive wheel illl from engagement with one wheel such as 38 to the othersuch as 99. The following positive impulses which are transmitted overthe line circuit 83 each time the escapement yoke,48 at the transmittingstation closes contacts 22l tariiy energize the relay 229 at thereceiving station, causing its tongu 23! to periodically engage its lefthand stop. As the tongue 23l engages the left hand stop, a circuit tothe magnet 12 is completed to reenergize the same. The

the armature lever 88 so that the projection 61 thereof, as hereinbeforedescribed, should it be in some other than the desired position. Thepositive synchronizing impulses will continue to be transmitted as longas the arm 222 of the switch 223 remains in its right hand stop. Themovement of the arm 222 to its left hand stop causes transmission ofnegative potential of the line conthe next time the contacts 22! areremain energized until the contacts 7 22i open to transmit a no-currentimpulse.

The deenergizamomene operates for each complete back and a resistance238 to a 53 to correct the position closed. This negative potential iseflected, as

hereinbefore described, to operat relays 226 and 223 to move the tonguesto their left and right hand stops, respectively, and complete circuitsto the clutch control magnets H2 and the magnets 12. This stops furtheroperation of the transmitting and receiving instruments with theirrespective elements in the same relative position.

If desired, the amplifiers 82 and 84 could be arranged to deletepredetermined of the regular positive synchronizing impulses so that themag net 12' at the receiving instrument would not be energized each timethe contacts 22l were closed. In this manner a synchronizing impulsewould be transmitted, for example, on each tenth oscillation of theescapement yoke 48 of the transmitting mechanism, or after any desirednumber as found necessary.

Another control circuit is shown in Fig. 8 which may be employed inconjunction with the differential correcting mechanism of Fig. 7. If itis assumed that the mechanism shown in Fig. 7 is a receiving instrument,that part of the circuit of Fig. 8 associated directly with thereceiving amplifier 84 would be employed to control the same. However,as will be evident hereinafter, mechanisms such as disclosed in Fig. 7may be employed as either a receiving or transmitting instrument. InFig. 8 the circuits at the transmittingend are substantially similar tothose at the transmitting station in Fig. l and like elements bearsimilar reference numerals. In Fig. 8 an additional set of contacts 233is added which are arranged to be closed when the escapement yoke 48 isin its right hand position. One of the springs of the contact set 233 isconnected to positive potential and the other in parallel with one ofthe springs of the contact set 224 is connected over the conductor 224to the coil of the relay 226. With the arm .222 of switch 223 on itsright hand stop, a. positive impulse will be transmitted over the linecircuit 83 for each stroke or movement of the escapement yoke 48. Thusand forth oscillation of the escapement yoke two positive impulses aretransmitted instead of the one impulse as in the system disclosed inFig. 1. At the receiving station these positive impulses are eilectiveon the relay 229, Fig. 8, to cause the tongue 23l thereof toperiodically moved from its center open line circuit position and engageits left hand stop. Such operation of relay 229 causes positivepotential from its tongue to be periodically applied to the inner tongueof a relay 234. The break stop associated with the inner tongue of relay234 is conneoted'by a conductor 236 through the left hand winding of adouble coil relay 23'! point 239, and thence throu h another resistance24! to negative potential at 242. The make stop of said inner tongue ofrelay 2341s connected through the winding of relay 234 and a resistance243 to the point 239 and over a parallel circuit including a conductor244, the right hand winding of relay 231 to a make stop thereof. Thetongue associated with said make stop of relay 23! is connected througha rectifier 248 to ground. The outer tongue of relay 234 is connected topositive potential and the associated break and make stops are connectedover individual circuits through the windings of the left and right handmagnets I43 assoelated with the yoke 48' to ground.

a The right hand stop 'of the tongue 23! of relay 228 in Fig. 8 isconnected through the winding oi relay 232 to ground, the associatedtongues of ,coil of relay 231 and which have positive potential appliedthereto. On the energization of relay 232 a circuit is completed to theassociated clutch control magnet. I44 to energize the same and also theleft hand magnet I43 associated with the escapement yoke 48.

The energization of the clutch control magnet I44 operates the clutchI45, Fig. '7, to disengage the shaft I64 from the motor M and alsoprevents further rotation of the shaft. The energization of the lefthand magnet I43 moves the escapement yoke 48 to its left hand positionand holds the same there. With the magnets I43 and I44 energized, theassociated instrument is held in an unoperating condition. Thiscondition prevails when negative potential is applied over the linecircuit 83 from theleft hand stop of the switch 223 at the transmittingstation.

The positive impulses transmitted from the contacts 22I and 233 as theescapement yoke 48 at the transmitting station oscillates are effectiveto operate the escapement yoke 48 at the receiving station in a mannerhereinafter pointed out. These positive impulses move the tongue 229from its center open line circuit causing positive im-- of relayposition to its left hand stop, pulses to be applied to the inner tongueof relay 234. If relays 234 and 231 are assumed to be in a deenergizedcondition on. the receipt of such a positive impulse as the first at theinner tongue of relay 234, a circuit will be completed from said tonguethrough the left hand coil of relay 231, the-resistances 238 and MI at242. The completion of'the above circuitento negative potential yoke tomove to the right.

ergize'sathe left hand coil'of relay 231, causing its tongue-which isconnected through the rectifier 246 to" ground to engage its make stopand complete a' circuit from ground through the rectifier 243;- thetongue, make stop and right handcoil of relaylSl cOnduCtor ZM; the coilof relay 234, the resistance243 to-the point239 and thence throughresistance 24I to negative-potential at 242. By choosingsuitablevalues/for thieres istances 238, 24I and 243 in connection with theresistances of the coil of. relay 234 and the left hand coil of relay231, the potential at thepoint 239 when the above described circuit fromnegative potential at 242 to positive potential at the tongue 23! ofrelay 229 is completed will be zero or slightly positive with respect toground. As

the above circuit includes the rectifier246, no current will flowthrough the coil of relay 234 so long as the above mentioned conditionexists. However, when the tongue 23I of relay 229 leaves its left handcontact in response to the next open line condition, point 239 willbecome negative with respect to ground, causing current to pass throughthe rectifier 246, the tongue of relay 231, the right hand coil thereofand-coil of relay 234 to operate the relay 234 and to hold relay 231operated. The above circuit through the right hand the coil of relay 234is a locking circuit and maintains the said relay in an energizedcondition until conditions hereinafter described occur to deenergize therelays. Thus, the first positive impulse for example transmitted overthe line circuit 83 causes the relays 234 and 231 to become energizedand locked up.

Thus, in response to a positive relay 232 to the left hand magnet I43 ofthe escapement yoke. With relay 234 deenergized a parallel circuit tothe left hand magnet I43 is completed from the inner tongue of relay 232and make stop thereof. However, the operation of relay deenergization ofrelay 232 opens the two parallel circuits to the left hand magnet I43.The outer tongue of relay 234 contacting its make stop completes acircuit to the right hand coil I43, energizing the same and causing theescapement escapement yoke 4?) permits the associated ratchet wheel 41'to advance a half a tooth, whereupon operations hereinbefore describedare performed.

impulse transmitted over the line circuit 83 following the transmissionof negative potential, the escapement yoke 48' at the receivinginstrument moves from its normal left hand position into its right, handposition. This movement of the escapement yoke 48 is in timed relationto the first movement of the escapement yoke 48 at the transmittingstation, and hence the receiving and transmitting instruments areinitiated into operation in phase with one another.

As long as the escapement yoke 48 at the transmitting station is free tooscillate, positive impulses will continue to be transmitted over theline circuit 83, and if it is assumed that the first positive impulsecaused relays 234 and 23'! to operate and lock up the next positiveimpulse will these relays in a manner effect deenergization ofhereinafter described. As relay 234 is deener- I43 of the escapement thelefthand magnet capement yoke to move tothe left and permits rotation ofthe associated ratchet .wheel 41 another half tooth.

With relays 234 and 231 locked up, as hereinbefore described, the nextapplication of a posi- .tive impulse to-the inner tongue of relay 234establishes a .circuit stop and coil of relay 234, resistance 243 to thepoint 239, through resistance 24I to negativepotential at 242. Thiscircuit holds the relay 234 energized while at the same time theapplication of positive potential to the make stop of the inner-tongueof relay 234 is the locking current through the right handcoil ofrelay'23l, whereupon it releases and breaks the above mentioned lockingcircuit through the right handcoil of relay 231. The circuit through thecoil of relay 234 is maintained until the tongue 23! of relay 229 leavesits left hand stop Whereupon the relay 234 is deenergized and thetongues thereof return to their break stops. means of the relays 234 and231 connected in the manner described they are effective tocauseenergization of first one of the relays I43 and then:

the other in definite timed relation to the receipt of the-positiveimpulses over the line circuit 83. The alternate energization of themagnets M3 in timed relation to the oscillation of the escapement yoke43 at maintains the receiving instrument in synchrostruments, andalthough nism with the transmitting instrument.

Obviously, by arrangements .uch as described .above a singletransmitting mechanism could be employed to control. a plurality ofreceiving inthe synchronizing impulses were described as originating atthe transmitting instrument functions of the machines 234 practicallysimultaneously with the This operation of the through the associatedmake effective to neutralize Thus, by

the transmitting station which might originate under the above-describedcircuits could be reversed, or the receiving station could be employedfor transmitting and the transmitting station for receiving.Furthermore, both transmitting and receiving stations could function asreceiving stations with respect to the synchronizing impulsesindependently of either. From the preceding paragraphs it can be seenthat the present invention provides a novel facsimile system and twomodifications of apparatus that may be employed in conjunction with thenovel system. The preferred embodiment of the apparatus includes areversing mechanism or clutch for reversing the direction of movement ofthe scanning element at the desired time, while the modified embodimentof the apparatus provides a differential clutch r mechanism forcorrecting a scanning element driving means whenever necessary. Bothembodiments of the apparatus function on a time basis whereby theoperations of the transmitting and recording machines occcur. in a timedrelationship. The differential clutch operates in such a manner as toretard the back stroke of the faster scanning element for an interval oftime equal to twice the interval that the faster scanning element com-Dleted its forward stroke ahead of the corresponding stroke on the othermachine. For instance, if, as explained, the seaming element of arecorder driven through'a differential mechanism reaches the end of itsforward stroke before the scanning element on the transmitter reachesthe end of its corresponding forward stroke, the differential mechanismof the recorder operates in a reverse direction until the transmitterseaming element reaches the end of its forward stroke. At thebeginning-of the return stroke of theiransmitter scanning element thedifferential mechanism of the recorder resumes its forward direction,and the scanning element driven thereby its back stroke at the sameascavoe trol means, and means including said control means for reversingthe direction of movement of said scanning member following the movementthereof in either direction in said path for predetermined lengths oftime. I

3. In a facsimile system, a transmitting machine, a recording machinecontrolled thereby, scanning and recording elements respectively inofsaid'members back and forth through the same respective paths ofmovement, means for initiat- 'ingthe movement of said members in onedirection in respective paths in'timed relation, and means for reversingthe direction of movement of said membersin said paths in the same timedrelation regardless of the length of travel of said time that thetransmitter scanning element reaches the end of its eflect of stoppingthe driving means at dead recorder scanning element center for aninterval equal to twice the length of time it completed its forwardstroke ahead of the forward stroke of the transmitter, and in thismanner each line scanning stroke of the transmitter scanning element isjustifiedwith each corresponding line scanning stroke of the recorderscanning element. The justification of a scanning line in thetransmittingapparatus included in the preferred embodiment of theinvention with a corresponding line at the associated recordingapparatus is accom- Plished as described by reversing the direction ofthe scamiing elements in a timed relation.

It will be obvious, of course, that various modifications other thanthose shown, described and sug ested herein may be made withoutdeparting from the spirit or essential attributes of the invention, andit is desired, therefore, that only such limitations be placed thereonas are imposed by the prior art or are specifically set forth in theappended claims.

What'is claimed is: 1. In a facsimile machine, a scanning element, meansfor moving said scanning element in opposite directions through apredetermined path,

and means for reversing the direction of movement of said scanningelement at any point in said predetermined path.

2. In a facsimile machine, a scanning member, means for moving saidscanning member in opposite directions through the same path, a conbackstroke. This has the 1 members in said paths. I

5. In a facsimile system, a transmitting instrument and a receivinginstrument controlled thereby, scanning elements included insaidinstruments with associated rotatable driving means therefor, means fortransmitting synchronizing signals concomitantly with each revolution ofsaid transmitting scanning element driving means, means at saidreceiving instrument controlled by said synchronizinglmpulses andeffective after a predetermined part of a revolution of said receivinginstrument driving means to retard the same in amounts proportional tothe amount it is faster than the driving means for said transmittinginstrument whereby both or said rotatable driving means completerevolutions in the same length of time.

6. In a facsimile machine, a scanning member movable in oppositedirections in the same path as the scanning progresses and a controlmeans for reversing the direction of movement of said member atpredetermined intervals.

7. In a facsimile machine, a scanning member movable to and fro inopposite directions in the same path as the scanning progresses, andmeans dependent upon the length of timeof movement of said member in onedirection to terminate movement'thereof in said direction and initiatemovement in the pposite direction.

8. In a facsimile system, a transmitting machine and 'g receivingmachine controlled thereby, scanningelements included in said machines,driving means to move said elements in back and forth strokes alongscanning lines, and synchronizing means associated with said machines tocontrol the application of said driving means to said elements to movethe same in said back and forth strokes in such a manner that thelengths of each corresponding scanning stroke of said machines islustified.

9. In a facsimile system, a transmitting machine and a receiving machinecontrolled thereby, scanning elements included in said machines. arotatable scanning element driving means in each of said machines formoving said elements in back and forth strokes along scanning linesduring each revolution of said driving means, and means for neutralizingone of said driving means

